How many rooms in a house do people really watch movies in? A couple of bluetooth speakers covers the 95% case, and just using the crappy laptop speakers or use earbuds or headphones for the 5% case.
Of course it would be nicer if the laptop had better speakers in it, but there are always trade-offs to be made on cost vs benefit, and fairly cheap bluetooth speakers are a pretty good workaround for a lot of people.
Not sure why you call the macbooks speakers crappy, i would imagine most people would consider them good enough and be happy with then instead of dealing with external Bluetooth speakers and carrying them around with the laptop.
By a strange coincidence I'm also in the group of people using their Macbook Pro while sitting on the sofa, due to not having a tv. I wouldn't use a dedicated TV enough to justify having one.